Reading code is a good start, but I've found that it's not enough. When faced with an unfamiliar concept, I'm not sure whether it's an unfamiliar design pattern

Reading code is a good start, but I've found that it's not enough. When faced with an unfamiliar concept, I'm not sure whether it's an unfamiliar design pattern, a hacky kludge, or a special case to get around some quirk for a particular use-case. I've found that reading books—such as the Pragmatic Programmer series, Effective Java, and others—helps me to understand the rationale behind what otherwise seem like strange (sometimes even boneheaded) design decisions. Even oft-derided patterns (such as the "FooBuilderFactoryBuilder" so often seen in the Java world) make sense when understood in the context of the problems they're trying to address.